The field of the present invention relates to a method for mending a dent formed on a smooth outer surface of an aluminum alloy member which detracts from the appearance of the member, and more particularly, to a preferred method for mending the member when rectification of the dent from the backside of the member is difficult.
Generally, when a dent is formed on the body panel of an automobile an external force, a sheet metal working process is effected to hammer out the dent and recover, as close as possible, the original shape of the body panel. Once this has been achieved the dent remaining on the outer surface of the member is filled with putty to obtain a smooth outer surface. In some cases, however, the sheet metal working process cannot be applied because an associated member (an inner member) is positioned behind or attached to the back side of the body panel (an outer panel) in such a way that it encloses the space that exists there. This problem can be dealt with through a build up soldering process. The methods for mending a panel made of steel and a panel made of aluminum alloy through the build up soldering process are shown in the flow charts illustrated in FIGS. 1 and 2, respectively.
Soldering of aluminum alloy (throughout this specification, the term "aluminum alloy" should be defined to also include aluminum) is difficult as compared to soldering of other metals such as steel or the like due to the fact that an oxide coating film is liable to be formed on the surface of the base member. Therefore, it is a common practice to perform the soldering inside a furnace while maintaining a non-oxidizing atmosphere therein. In addition, the solder (brazing material) used in soldering of JIS 5000-series and 6000-series aluminum alloys has a high melting point (400.degree. C.-650.degree. C.). Hence these aluminum alloys cannot be soldered using the conventional process, but must be soldered using the TIG arc-welding process as shown in FIG. 2.
Both the method of effecting soldering within a furnace and the method of effecting soldering using the TIG arc-welding process, require a special installation. That is, in the former method, if the size of the object is large, a large furnace is required, while in the latter method, at least two other shortcomings exist: .circle.1 as the quantity of heat injected into the base member increases, not only does the thermal strain in the base member increase detracting from the appearance of the member but, in addition, the crystalline grains in the base member grow coarser reducing its rigidity and .circle.2 the thickness of the build up soldering has a limit of about 2 mm, while the thickness of the putty has a limit of about 3 mm, and hence, in the event that the depth of the dent in the base member exceeds 5 mm, the dent cannot be dealt with through this method.
Thus mending the dent on an aluminum alloy member by build up soldering cannot easily be achieved using the prior art method.